1. Technical Field
Aspects of the present invention relate to an image formation device.
2. Related Art
Image formation devices configured such that a plurality of image forming units of different colors are arranged along a lengthwise direction of a belt for conveying a sheet of paper and toner images respectively corresponding to the image forming units are formed on the sheet of paper being conveyed on the belt have been widely used. If displacement occurs between image formation positions of the image forming units, the image quality on the sheet of paper deteriorates.
Japanese Patent Provisional Publication No. 2002-91115 discloses an example of an image formation device which employs a technique (a so-called registration) for correcting displacement of image formation positions. One of factors causing such displacement of image formation positions is unevenness of the thickness of the belt. Since displacement due to unevenness of the thickness of the belt (i.e., variations in moving speed of the belt) occurs in a cycle period equal to the entire length of the belt.
Therefore, in a general registration scheme, a correction pattern formed of a plurality of marks having different colors is formed along the entire length of the belt, displacement between the marks of different colors is measured, and an average of the displacement is obtained for each color. By correcting the image formation position of each color based on results of the measurement, deterioration of the image quality can be prevented and thereby the print quality can be maintained.